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De Boer, E., Ockeloen, C. W., Kampen, R. A., Hampstead, J. E., Dingemans, A. J. M., Rots, D., Lütje, L., Ashraf, T., Baker, R., Barat-Houari, M., Angle, B., Chatron, N., Denommé-Pichon, A.-S., Devinsky, O., Dubourg, C., Elmslie, F., Elloumi, H. Z., Faivre, L., Fitzgerald-Butt, S., Geneviève, D. and 30 moreDe Boer, E., Ockeloen, C. W., Kampen, R. A., Hampstead, J. E., Dingemans, A. J. M., Rots, D., Lütje, L., Ashraf, T., Baker, R., Barat-Houari, M., Angle, B., Chatron, N., Denommé-Pichon, A.-S., Devinsky, O., Dubourg, C., Elmslie, F., Elloumi, H. Z., Faivre, L., Fitzgerald-Butt, S., Geneviève, D., Goos, J. A. C., Helm, B. M., Kini, U., Lasa-Aranzasti, A., Lesca, G., Lynch, S. A., Mathijssen, I. M. J., McGowan, R., Monaghan, K. G., Odent, S., Pfundt, R., Putoux, A., Van Reeuwijk, J., Santen, G. W. E., Sasaki, E., Sorlin, A., Van der Spek, P. J., Stegmann, A. P. A., Swagemakers, S. M. A., Valenzuela, I., Viora-Dupont, E., Vitobello, A., Ware, S. M., Wéber, M., Gilissen, C., Low, K. J., Fisher, S. E., Vissers, L. E. L. M., Wong, M. M. K., & Kleefstra, T. (2022). Missense variants in ANKRD11 cause KBG syndrome by impairment of stability or transcriptional activity of the encoded protein. Genetics in Medicine, 24(10), 2051-2064. doi:10.1016/j.gim.2022.06.007.
Abstract
Purpose
Although haploinsufficiency of ANKRD11 is among the most common genetic causes of neurodevelopmental disorders, the role of rare ANKRD11 missense variation remains unclear. We characterized clinical, molecular, and functional spectra of ANKRD11 missense variants.
Methods
We collected clinical information of individuals with ANKRD11 missense variants and evaluated phenotypic fit to KBG syndrome. We assessed pathogenicity of variants through in silico analyses and cell-based experiments.
Results
We identified 20 unique, mostly de novo, ANKRD11 missense variants in 29 individuals, presenting with syndromic neurodevelopmental disorders similar to KBG syndrome caused by ANKRD11 protein truncating variants or 16q24.3 microdeletions. Missense variants significantly clustered in repression domain 2 at the ANKRD11 C-terminus. Of the 10 functionally studied missense variants, 6 reduced ANKRD11 stability. One variant caused decreased proteasome degradation and loss of ANKRD11 transcriptional activity.
Conclusion
Our study indicates that pathogenic heterozygous ANKRD11 missense variants cause the clinically recognizable KBG syndrome. Disrupted transrepression capacity and reduced protein stability each independently lead to ANKRD11 loss-of-function, consistent with haploinsufficiency. This highlights the diagnostic relevance of ANKRD11 missense variants, but also poses diagnostic challenges because the KBG-associated phenotype may be mild and inherited pathogenic ANKRD11 (missense) variants are increasingly observed, warranting stringent variant classification and careful phenotyping. -
Watson, L. M., Wong, M. M. K., & Becker, E. B. E. (2015). Induced pluripotent stem cell technology for modelling and therapy of cerebellar ataxia. Open Biology, 5: 150056. doi:10.1098/rsob.150056.
Abstract
Induced pluripotent stem cell (iPSC) technology has emerged as an important tool in understanding, and potentially reversing, disease pathology. This is particularly true in the case of neurodegenerative diseases, in which the affected cell types are not readily accessible for study. Since the first descriptions of iPSC-based disease modelling, considerable advances have been made in understanding the aetiology and progression of a diverse array of neurodegenerative conditions, including Parkinson's disease and Alzheimer's disease. To date, however, relatively few studies have succeeded in using iPSCs to model the neurodegeneration observed in cerebellar ataxia. Given the distinct neurodevelopmental phenotypes associated with certain types of ataxia, iPSC-based models are likely to provide significant insights, not only into disease progression, but also to the development of early-intervention therapies. In this review, we describe the existing iPSC-based disease models of this heterogeneous group of conditions and explore the challenges associated with generating cerebellar neurons from iPSCs, which have thus far hindered the expansion of this research.
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